Children – especially African Americans – who live in disadvantaged neighborhoods have consistently low levels of the stress hormone cortisol, according to a study that examined children in Alabama.

Cortisol is an important stress hormone associated with good physical and mental health and well-being. The low levels of cortisol measured in the study were in children living in neighborhoods with high unemployment, poverty, female heads of households and vacant housing.

The study’s findings are significant because extended exposure to low cortisol levels may increase immune responses, leading to inflammation and the risk for some chronic childhood diseases. The results add more details to a growing number of reports that link exposure to chronic stressors – including noise, violence and poverty – to negative health effects, such as asthma.

The body’s mechanism for dealing with stress is one explanation for the links. When exposed to a stressful event, a hormonal signaling system called the hypothalamic-pituitary-adrenal axis – or HPA axis – causes cortisol hormone to be released into the bloodstream. However, long-term chronic exposure to stress can disrupt the normal functioning of the HPA axis and result in an opposite reaction – lower than normal levels of cortisol.

In this study, researchers at the University of Alabama at Birmingham recruited 148 African and European-America children about eight years of age. Children were seen up to five times during a period of nine years. At each study visit, cortisol was measured in the children’s blood samples. Unemployment, poverty, female-headed households with children and vacant houses were used to determine neighborhood environments. Researchers adjusted for differences, including age, weight, gender and other personal factors.

Overall, children who lived in disadvantaged neighborhoods had lower levels of cortisol. When the researchers looked closer at the role of race on the results, they found that the association between neighborhood and decreased cortisol was greatest in African-American children. The trend between disadvantaged neighborhoods and decreased cortisol was evident in European-American children, but was not as strong and could be due to chance. Gender did not appear to play a role in the levels of cortisol.

The results demonstrate that the physical environment in which children are raised plays an important role in their well-being. In addition, the measure of cortisol provides objective evidence of the body’s physiologic response to chronic stress, which has previously been shown to be associated with health effects including childhood asthma.